The device relates to “active implantable medical devices” as defined by the Directive 90/385/EEC of 20 Jun. 1990 the Council of the European Communities. More specifically, the device relates to implants to continuously monitor heart rhythm and which are capable of delivering to the heart electrical pulses for stimulation, resynchronization and/or defibrillation in case of arrhythmia detected by the device.
The device also relates to the diagnosis of atrial contraction disorders. These disorders usually appear as aftermath of an episode of atrial fibrillation (AF). Atrial fibrillation is an arrhythmia characterized by abnormally high frequency of the atrial rhythm. Atrial contraction disorders may also result from other conditions such as atrial ischemia or dilated atrium by sarcoidosis or fibrosis. After an episode of AF, the contraction of the myocardium at the atrium is deficient or absent, despite the presence of a spontaneous or stimulated observable electric depolarization wave. An atonic atrium muscle leads to a lower contribution from the atrium muscle to fill the ventricle. This results in a very marked deterioration in hemodynamic performance. In such a situation, it may not be possible to optimize a double chamber operation of a device with atrial and ventricular sensing and ventricular stimulation. In this mode, the device triggers when ventricular pacing may be required or desirable after a predetermined atrioventricular delay (AVD). The AVD is counted from the detection of a spontaneous or paced atrial event. This AVD is normally adjusted to optimize the overall functioning of the heart from the hemodynamic point of view. In the case of atrial atony, the normal electrical activity causes the application of the AVD. However, it is challenging to optimize this delay because the actual behavior of the atrium is not known.
With the exception of an exploration by echocardiography, it is challenging to determine whether, after an episode of AF, a patient has recovered to normal mechanical atrial activity. It is also challenging to determine when that recovery has occurred. Furthermore, it is challenging to determine if there is an atrial atony, an absent or deficient contraction of the atrium despite an observable electrical activity (sinus rhythm).